Surface Code Entanglement Ejection

Scaling fault-tolerant quantum computing beyond a single processor demands logical - logical entanglement. While surface codes excel in local error correction, creating robust, distributed entanglement remains challenging. In this work, we introduce Entanglement Ejection - a protocol for generating physical - logical entanglement from a single logical qubit. This subroutine establishes logical - logical entanglement via entanglement swapping with a physical Bell pair provided by a quantum network. Unlike common injection-based methods, our protocol is deterministic, requiring no post-selection and thereby has the potential of reducing spatio-temporal resource overhead. We show via numerical simulations under a superconducting-specific noise model that this potential resource efficiency comes at the cost of a slightly higher, yet comparable, logical error rate.